Fungal infections Flashcards
Define what candida, candida spp and candidiasis is
- Candida” is a genus of parasitic, yeast-like fungi
- Candida “spp.”(meaning several species of candida)•
- “Candidiasis” – an infection of skin or mucosa caused by acandida (usually C.albicans – causes thrush)
Briefly talk about candida spp
- Oral Candidiasis is caused by intra-oral commensal yeasts. (>80% C. albicans)
- All oral candidal infections are opportunistic in nature.
Describe candida albicans
- C.albicansis the most virulent Candida spp.in humans
- A characteristic feature of C.albicans is its ability to form true hyphae.
- These hyphae penetrate through the tissue and obtain nutrients through that
Describe opportunistic infections
- When a harmless commensal of the oral cavity transitions to a pathogen – resulting in disease
- Disease is a result of an imbalance between fungal virulence factors and host defenses
- Commensal Fungi are normally kept under control through specific and non-specific host defence mechanisms
- Competition of other micro-organisms –e.g. bacteria.
List 6 local predisposing factors for a candidal infection
- Prostheses – changes in environmental conditions, trauma, denture usage, oral hygiene
- Saliva quality (↓pH, ↑glucose concentrations)
- Saliva quantity (Salivary hypofunction, Sjogren’s Syndrome, Radiotherapy, Drug Therapy)
- Commensal Flora – e.g. modified by broad-spectrum antibiotics
- High-Carbohydrate diet
- Smoking
List 6 systemic predisposing factors for a candidal infection
- Physiological – e.g. pregnancy, extremes of age - neonates/elderly
- Endocrine disorders – e.g. Diabetes Mellitus
- Nutritional deficiencies – e.g. Fe, Folic Acid, Vitamin B12
- Malignancies – e.g. leukemia, agranulocytosis
- Primary immunodeficiency – e.g.DiGeorge’s Syndrome
- Secondary immunodeficiency – e.g.HIV, corticosteroids, anti-cancer therapies
List 4 ways that saliva can prevent a candidal infection
- Prevents oral colonization and invasion of candida spp.
- Removes unattached or poorly adherent candida spp
- Inhibits candidal adhesion to host surfaces by Salivary IgA.
- Candidacidal activity due to anti-fungal proteins (histatins, defensins, lysozymes)
Explain 3 ways that diabetes mellitus contributes to candidal infections
- ↑ Salivary glucose levels
- ↓ Neutrophil function due to hyperglycaemia
- Uncontrolled DM is a major predisposing factor in Aspergillus– especially complicated by diabetic ketoacidosis.
Explain the significance of candida in HIV patients
- Oral candidiasis is a universal finding in patients with severe cell-mediated (T-cell) immunodeficiencies – i.e.HIV/AIDS.
- Up to 90% of HIV-infected patients develop oropharyngeal candidiasis at some point during the progression of their disease
- Oropharyngeal candidiasis can be used as a predictor for the progress of HIV infections in affected individuals.
List 4 things that can lead to secondary immunosuppression
• Solid Organ Malignancies –e.g. Lymphoma
• Haematological
• Malignancies – e.g. Leukaemia
• Cytotoxic Chemotherapy
Topical and Systemic
• Corticosteroids and other Immunomodulatory Drugs
List the types of oral candidiasis
Primary Oral Candidiasis
• Pseudomembranous Candidiasis (Acute and Chronic)
• Erythematous Candidiasis (Acute and Chronic)
• Chronic Hyperplastic Candidiasis
Candida-associated Lesions • Angular Cheilitis • Median Rhomboid Glossitis • Denture-associated Erythematous Stomatitis • Linear Gingival Erythema
Secondary Oral Candidiasis
• Chronic Mucocutaneous
• Candidiasis
Describe pseudomembranous candidiasis in terms of:
- Appearance
- Symptoms
- Who it occurs in
- Places of occurrence in acute and chronic forms.
Description
• Also known as “oral thrush”.
• Semi-adherent, whitish, soft, creamy drop-like patches.
• They can be removed, leading to a red and slightly bleeding surface
Symptoms
• Lesions are usually asymptomatic, although sometimes patients may complain of burning and dysphagia
Who it occurs in
• The lesions may recur in patients using corticosteroids topically or by aerosol, in HIV patients or immunocompromised patients
Places of occurrence
• Acute Form: Palate, Dorsum of Tongue, Buccal Mucosa
• Chronic Form: Palate, Dorsum of Tongue, Oropharynx.
Explain erythematous candidiasis in terms of description and places of occurrence
- May present as an acute or chronic form
- Erythematous areas often associated with topical or systemic corticosteroid use, broad-spectrum antibiotic therapy or HIV disease
- Painful
- Can affect any part of the oral mucosa – but typically affects the dorsum of the tongue, palate.
Describe chronic hyperplastic candidiasis in terms of:
- Appearance
- Presentations
- Places of occurrence
- Histology
Appearance
- Characterized by adherent white lesions ranging from small translucent to large opaque plaques.
- Hyperplastic candidiasis lesions are not scrapable.
Presentations
Two variants
• Homogenous
• Nodular/Speckled
Places of occurrence
• Affects commissures of the mouth, less commonly on the buccal mucosa,palate, tongue
• This form may require a biopsy; as it is associated with varying grades of dysplasia
Histology:
• Parakeratosis, and hyperplastic epithelium, with inflammatory infiltrate and candidal hyphae invasion to the upper layers of the epithelium.
Describe angular cheilitis, list the responsible candida spp and list 6 predisposing factors
- A chronic inflammatory lesion of thelabial commissures
- May be unilateral or bilateral
- Usually symptomatic, both skin and oral mucosa may be affected
- May have a tendency to bleed
- Candida spp and S. aureus are considered the cause of the lesions.
Other predisposing factors: • Anaemia • Vitamin B12 deficiency • Immunodeficiency • Reduced vertical dimension • Lip-licking • Thumb-sucking habits
Describe median rhomboid associated lesions
- Erythematous atrophic area; “rhomboidal” in shape and located on the posterior-midline part of the dorsum of the tongue; just slightly anterior to the circumvallate papillae
- Often asymptomatic
- Candida sppare frequently isolated from the lesion
- BUT – little evidence that these lesions resolve after topical anti-fungal therapy.
Describe denture- associated erythematous stomatitis and potential causes
- Chronic erythema affecting almost exclusively the palatal mucosa and alveolar ridges which are in contact with the fitting surface of a denture
- Exact aetiopathogenesis is unknown
- Commensal candidal overgrowth + poor oral and dental hygiene, night-time denture wear, and poor fitting dentures.
Describe linear gingival erythema
- Anon-plaque induced localized orgeneralized gingivitis found predominantly in HIV patients
- Likely a combined bacterial and fungal opportunistic infection
- Distinct erythematous band of 2-3mm width along the gingival margin
- May be associated with discomfort and occasional bleeding.
- Thought to be an HIV-associated periodontal lesion, together with necrotizing ulcerative gingivitis and periodontitis.
Describe a secondary oral candidal lesion called chronic mucocutaneous candidiasis and list its 3 main types
- Persistent or recurrent candidal infections of the oral cavity and other sites of the body.
- Infections of the oral cavity (90%), may involve pharynx and larynx
- Frequent cutaneous and vulvovaginal involvement.
Three main types
• Familial CMC
• Diffuse-Type CMC
• Endocrine Candidiasis Syndrome
Describe deep fungal infections
- Deep Fungal Infections are considered as systemic mycoses, but the orofacial area may also be involved with intra-oral manifestations.
- Aspergillosis is the second most prevalent opportunistic mycotic infection after candidiasis
- High mortality rate in the paediatric population (~85%)
- Mucormycosis is also a common invasive fungal infection affecting immunosuppressed patients.
- Mortality rate 20-50%
Describe aspergillosis
- Caused by a fungus called Aspergillus (e.g. Aspergillus fumigatus, Aspergillus flavus) that is present in the environment. It is usually inhaled.
- Usually affects healthy individuals
- May present as a non-invasive disease - “mycetoma” – a mass of fungal organisms within a body cavity – e.g. maxillary sinus.
- Aspergillosis can develop after dental procedures – e.g.extractions, endodontic therapy involving the posterior maxillary region
- May appear as gingival ulceration and palatal swelling with a grey to violaceous hue
Describe mucormycosis
- Caused by the fungi within the subphylum mucormycotina.
- Infection starts in the paranasal sinuses and often spreads rapidly onto adjacent structures such as the palate, cavernous sinuses, orbits and cranium
- Patients may have nasal obstruction, nasal discharge including blood, facial pain, headache, cellulitis, visual disturbances and seizures
- In early stages of disease - Intra-oral examination may show swelling of the palate/maxillary alveolar process
- If left untreated – may develop palatal ulceration, oronasal fistula, frank necrosis, and massive tissue destruction
Describe blastomycosis
- Blastomycosis is caused by Blastomyces Dermatitidis
- Infection occurs via inhalation of spores.
- Mainly affects the lungs, may spread to the skin, bones/joints and genitourinary tract
- Intra-orally - may exhibit a gradually enlarging ulcer with a rolled border or an erythematous nodule with a granular/warty surface
- May spread to the underlying maxilla/mandible
Describe histoplasmosis
- Histoplasmosis – caused by Histoplasma capsulatum
- Inhalation of airborne spores from disrupted soil often enriched with guano
- Most infected individuals are asymptomatic
- Severe pulmonary disease occurs with immunocompromised patients; and may disseminate
- Oral lesions typically appears a solitary chronic ulcer with a rolled margin
- Oral lesions may mimic the appearance of squamous cell carcinoma.
